Thinking outside the Thinking outside the river basinriver basin

Regional and global impacts of river Regional and global impacts of river impoundments and withdrawalsimpoundments and withdrawals

Christopher E. WilliamsChristopher E. WilliamsCarissa WongCarissa Wong

WWFWWF

Resource extractionPoor governance

Inter-basin transfers

Poor agricultural practices

Dams

Point and non-point source pollutionConversion of wetlands

Dredging and canalisation

Run-off fromhuman settlements

Poor fisheries managementClimate change

Impacts of impoundments and Impacts of impoundments and withdrawals on river systemswithdrawals on river systems

a)a) alter the downstream flux of alter the downstream flux of water and water and sedimentsediment, which modifies biogeochemical , which modifies biogeochemical cycles as well as the structure and dynamics of cycles as well as the structure and dynamics of aquatic and riparian habitats aquatic and riparian habitats (abiotic exchange) (abiotic exchange)

b) change water b) change water temperaturestemperatures, which influence , which influence organismal bioenergetics and vital ratesorganismal bioenergetics and vital rates””

c) create barriers to upstreamc) create barriers to upstream--downstream downstream movement of movement of organismsorganisms and nutrients, which and nutrients, which hinders biotic exchange (hinders biotic exchange (biotic exchangebiotic exchange))

Source: Poff and Hart (2002)Source: Poff and Hart (2002)

ThatThat’’s a lot of waters a lot of water……

Between 1972 and 1991 the amount of water Between 1972 and 1991 the amount of water impounded doubled.impounded doubled.

Today, impoundments total approximately Today, impoundments total approximately 337,000 km2 globally.337,000 km2 globally.

If put together, these impoundments would If put together, these impoundments would form a body of water over four times larger form a body of water over four times larger than Lake Superior.than Lake Superior.

Sources:Sources: Chao 1991Chao 1991Downing 2006Downing 2006

“…“…an important unresolved question is whether the an important unresolved question is whether the cumulative effects of dams are inducing continental to cumulative effects of dams are inducing continental to global scale convergence of historically distinctive global scale convergence of historically distinctive regional environmental templates, thereby diminishing regional environmental templates, thereby diminishing regionalregional--scale variation that helps maintain broader scale variation that helps maintain broader patterns of native biodiversity.patterns of native biodiversity.””

Source: Poff et al. (2007)Source: Poff et al. (2007)

YangtzeYangtze

Turning up the heat on Turning up the heat on JapanJapan

Trouble in the food Trouble in the food chain?chain?

Aggravating global Aggravating global climate changeclimate change

NileNile

Sending a chill Sending a chill through the through the FrenchFrench

Reducing fish Reducing fish stocks in the stocks in the Eastern Eastern MediterraneanMediterranean

The Seas of EuropeThe Seas of Europe

““It is clear thatIt is clear that……changes to the global changes to the global water system are now globally significant water system are now globally significant and are being modified without adequate and are being modified without adequate understanding of how the system works. [ ] understanding of how the system works. [ ] What are the magnitudes of anthropogenic What are the magnitudes of anthropogenic and environmental changes in the global and environmental changes in the global water systemwater system……??”” (Global Water Systems (Global Water Systems Project)Project)

What are the implications for policy, What are the implications for policy, governance, and management?governance, and management?

Traditionally, basin management Traditionally, basin management agreements are between basin states agreements are between basin states only. This may need to be reconsidered.only. This may need to be reconsidered.Global agreements may take on more Global agreements may take on more relevancerelevanceGlobal impacts may spur global action Global impacts may spur global action (think climate change)(think climate change)

Thinking about environmental flows Thinking about environmental flows in a different context.in a different context.

AcknowledgementsAcknowledgements

Carissa WongCarissa WongFlavia LouresFlavia LouresMichele TheimeMichele TheimeLara HansonLara HansonGlobal Water System Global Water System ProjectProject

Thank you.Thank you.